In the past and continuing up to the present, a common technique of providing message service for telephone users has been to utilize message answering bureaus. In some cases, all calls to a principal station are routed to an answering service where messages are manually taken. In other cases, call routing to an answering service is automatic after a prescribed number of unanswered rings at a principal station. In either event, the principal must call the answering service to obtain from an operator a recitation of messages that may have been received.
Messages are typically received by a secretary or an answering bureau in customer premises types of telephone equipment such as private branch exchanges (PBXs) or key systems. We refer herein to parties for whom messages are taken as principals and to their telephone stations or principal stations. In some cases, a message waiting (MW) lamp is provided at principal stations. Typically, such a lamp is manually activated by pushing a button at an operator's console. Alerted by activation of the MW lamp, the principal calls the appropriate party to obtain messages and then manually deactivates the MW lamp by depressing a button at the principal station.
More recently, systems are becoming available which automate the storing of callback types of messages and the activation and extinguishing of MW lamps associated with stations. This type of operation is described in a U.S. patent application Ser. No. 363,469, filed by J. L. Cottrell et al on Mar. 30, 1982 now U.S. Pat. No. 4,476,349. This system provides a feature called Leave Word Calling (LWC), which automatically generates and stores a callback message for a called principal station on demand from a caller or other party associated with a call. In addition, a message center service is alternately available in which an operator verbally receives a message and enters the message into storage from an operator terminal. In either case, the system activates an automatic message waiting (AMW) lamp at the intended principal station in response to the storage of the message. Stored messages are retrieved by the principal or other authorized party by means of special station equipment. In the referenced system, stored messages are deleted from storage only on explicit request from the message retriever and not by virtue of being merely accessed. One reason for this is to provide rincipals with a convenient repository for messages on which the principal does not wish to act immediately. Another reason is that there is no convenient way to guarantee that a message is actually seen by a principal merely because the message is transmitted by the system toward the special message acccessing equipment. The AMW lamp at a principal station is activated when stored messages are present and is automatically extinguished by the system when there are no more messages stored in the system for the principal.
Experience with the above system has shown that, as a practical matter, AMW lamps are virtually always activated, both because of use of the message storage service by principals to retain old messages as reminders for future action and because there are several sources of message generation. Thus, the message alerting function becomes much less useful than might otherwise be expected because of the fact that AMW lamps are usually lit. Moreover, new message services are likely to be forthcoming as systems mature into even more advanced systems, thus further vitiating the usefulness of the message alerting function.
While the system disclosed in the Cottrell et al application offers significant advantages over the prior art, improvement is needed in the area of automatic message waiting alerting.